A Design Of Signal Generating Module And Frequency-sweeping Module Based On FPGA

Adaptive optics is one of contemporary optics frontiers and it is mainly used for correcting the optical phase difference and has achieved good results in the laser beam cleanup, beam control, atmospheric laser communications and other fields. Adaptive optics system is a complex closed-loop system and when the system fails, it is often not easy to quickly test out the causes of system failure. So our team designed an FPGA-based digital test platform to quickly and efficiently test the system’s operating conditions, such as testing voltage characteristics of drives of the deformable mirror and the frequency response characteristics of the system. This required test platform to design sweep signal generator, single-frequency signal generator and a multiplexer module that can be configured for frequency- sweeping. However, the conventional DDS sweep signal generator exists high ROM occupies and poor accuracy of output signal. And traditional DDS single-frequency signal generator also exists high ROM occupies, and the output signal is spurious. Further, conventional swept module can only measure a single path. But for the adaptive system, its deformable mirror has tens to hundreds of drives, so we need to design a digital multi-channel module that can be configured to sweep. To this end, this paper designed an FPGA-based signal generation module and frequency-sweeping module. Signal generation module includes the design and implementation of high-precision three-addressing sweep signal generator and low spurious single frequency signal generator. And sweep module is a fully digital multi-channel configurable sweep module.Simulation results show that the generated sweep signal ranges from 0Hzto 1000 Hz. The traditional program uses 16-bit ROM and three-addressing high-precision sweep signal generator uses(2,8,6) program. Compared with traditional program, three-addressing high-precision sweep signal generator’s output sweep signal has an improve of accuracy of 26.192 percent. But, three-addressing high-precision sweep signal generator only occupies 1/64 ROM of the traditional scheme. In addition, the simulation results show that low spurious single frequency signal generator’s spurious output signals are significantly reduced, compared with the traditional single-frequency signal generator. In addition, the frequencysweeping module can measure multiplexed sweep frequency response characteristics.